The invention relates to an active matrix organic electroluminescent device and, more particularly, to a full-color active matrix organic electroluminescent device with color filters.
Several methods have been employed to achieve full color emission in organic electroluminescent devices. In general, full color organic electroluminescent devices are fabricated by a method of RGB emitting layers or color changing method. Among them, the so-called “color changing method” involves forming white organic light-emitting diodes respectively on corresponding red, green and blue color filters, and then driven by bias voltages to emit red, green and blue respectively.
FIG. 1 is a cross section illustrating a conventional full-color active matrix organic electroluminescent device having a color filter on array (COA) structure. The full-color active matrix organic electroluminescent device 10 includes a substrate 12, a plurality of TFTs 20, RGB color filters 32, 34, and 36, and a plurality of white organic light-emitting diodes 40, wherein each white organic light-emitting diode 40 comprises a ITO electrode 42 formed on the color filters 32, 34, and 36 to achieve electrical connection with the TFT 20. The light emitted from the white organic light-emitting diode 40 is converted to RGB by passing through the RGB color filters 32, 34, and 36.
FIG. 2 is a close-up cross-section view of location A shown in FIG. 1. Since the color filters 32, 34, and 36 have top surfaces 37 with severe surface roughness of around 20 nm, the direct deposition of the subsequent ITO electrode 40 may result in a rough surface 43 with a surface roughness also around 20 nm. Therefore, in addition to failing to fulfill the requirements of an organic electroluminescent device with a preferred surface roughness of the electrode less than 10 nm, current-leakage and point discharge may also occur, adversely affecting luminance efficiency and product life.
Moreover, the color filter typically comprises organic compounds, such as organic dyes or resins, and has a thermal decomposition temperature of about 350° C. If the following ITO electrode is directly formed on the color filters by a thin film process with a high operating temperature of more than 400° C. (such as by chemical vapor deposit (CVD)), the top portion of the color filters can thermally expand or decompose due to high operating temperature, resulting in damage to the color filters.
Therefore, it is necessary to develop a simple and efficient manufacturing method for an OLED with a color-filter-on-array structure to obtain OLEDs having smoother transparent electrode surfaces.
Several difficulties exist which must be overcome by full-color active matrix organic electroluminescent devices in order to meet the demands of the flat panel display market. Therefore, it is necessary to develop a simple and efficient manufacturing method and structure for a full-color active matrix organic electroluminescent device to increase the performance and reliability thereof.